| Dust aerosol accounts for about half of the total atmospheric aerosol,whic h not only affects the weather and climate,but also plays an important role in marine ecology and global material circulation.Research shows that the contri bution to atmospheric dust aerosol of dust devil should not be ignored.The tot al amounts of atmospheric dust aerosol over the deserts are the result of the j oint action of dust devil and dust weather.The Taklimakan Desert is one of th e major dust sources in China and East Asia.However,the lack of systematic study on the dust devil emission processes caused poor understand on the cha racteristics and contributions of dust devil emission,and led to underestimate t he amount of dust emission of the Taklimakan Desert.In view of this,based on the observed data of meteorology and dust devil in the desert transition zon e on the northern margin of Taklamakan Desert,the climatic characteristics of dust devil are analyzed,the formation mechanism of dust devil is discussed,an d the calculation model of dust devil emission is modified using the observed data,as well as the contribution of dust devil to the dust emission amount in the study area is given quantitatively,and the results are as follows:(1)The occurrence days of dust devil in the study area showed an overall fluctuating and decreasing trend from 1992 to 2017;spring,summer,autumn and winter accounted for 37.88%,48.75%,9.25%and 4.13%of the total occurrence days,respectively,among which spring and summer accounted for 86.62%of the total occurrence days;the daily occurrence times of dust devil in the study area showed a significant unimodal distribution,which began to appear at 9:00,and basically none were observed after 18:00,with a peak from 14:00 to 1500,accounting for 19.7%of the total number of occurrences,as well as the duration was generally short,that is,72.5%of dust devil lasted less than 10 minutes,and those between 10 and 16min accounted for 21.6%of the total and only 5.9%of the total lasted longer than 16min.(2)The occurrence days of dust devil are closely related to meteorological elements,and the monthly occurrence days of dust devil have a preferable positive linear correlation with the temperature difference between the surface and 2m height,the correlation coefficient r is 0.875;have a better power function correlation with wind speed,and the correlation coefficient R2 is 0.880;have a good negative linear correlation with relative humidity,and the correlation coefficient r is-0.869;have a better negative linear correlation with air pressure,and the correlation coefficient is-0.976,and all of them have passed the significance test of 0.01.(3)The parameterization scheme of dust devil emission was improved bas ed on observed data.After improvement,the yearly total number of dust devil is 431,which is 55.2%more than that before improvement;the yearly total s and emission times of dust devil is 181.28 hours,which is 95.9%less than th e daylength time before the improvement,and 31.8%more than the sunshine ti me;and the yearly total sand emission amount of dust devil is 15.28t,which i s 95.2%less than that before improvement.(4)The total dust emission amount per square kilometer in the study area is15.28 t,1.54 t in spring,12.58 t in summer,1.16 t in autumn and 3.56×10-3 t in winter,accounting for 10.08%,82.32%,7.58%and 0.02%of the total in the whole year,respectively;the total annual dust emission amount of sand and dust weather per square kilometer is 17.72 t,and is 6.55 t,10.89 t,0.27 t and 0.0011 t in spring,summer,autumn and winter,respectively,accounting for 36.96%,61.46%,1.52%and0.006%of the total,respectively.(5)The total dust emission amount generated by dust devil and sand and dust weather in the study area.The total annual that per square kilometer is 32.99 t,and that in spring,summer,autumn and winter is 8.09 t,23.47 t,1.43 t and 0.05×10-1 t,accounting for 24.52%,71.14%,4.33%and 0.01%of the total,respectively,among which the contribution rate of dust devil and sand and dust weather is 46.30%and53.70%,respectively. |
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